Lets see,Broncow72 posted the link to the step tool. Mark Troy, thats what mine looks like. The one on the link is real cheap too.
Broncow72 the void you asked about was a concern of mine too. I punched 3 plug weld holes in the panel end. I shaped a peice of sheet metal to fit the space, next I bent a 90 on it and slid the whole piece behind the panel. This filled the hole/space. I plug welded the angle to the panel to lock it in place. I also seam sealed it from the inside, before I put on the end cap / tail light piece. So I think I got that part covered.
Brian wanted to see welds, nothing like being called out, Im not bragging, their not great but they cleaned up good.
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